Often, farmers fall into the trap of only looking at how to get fertility into a plant, and they end up not looking closely enough at how the soil itself can support that goal. The potential of land is much higher than what most people give it credit for. It doesn’t matter if you have light, sandy soils or heavy, black clay-based ground – most land still has the capability of supporting even better crops.

Heavy soil on farms is often referred to as the “good” soil, but it’s not because most of those soils are at their top potential. More often it’s because the heavier soils hold more water and nutrients. You’re more or less using up what’s already there, whereas on sand there’s not as much to use up. It comes down to the speed of responsiveness to fertility. Once you measure what you have and compare that to what you need to achieve your potential, sandy soils turn out to be a faster responder as a general rule than clay soils, especially if those clay soils are already producing what would be considered good yields. I’ve worked with farmers who are amazed at how fast they can get crops to respond on sandy soils. On heavy soils, you have to use a slower process, but I regularly see farms where the sands with corrected fertility outyield the heavy ground.

The key is getting everything there in the proper order.

I’ve found that what’s really restricting soils and agricultural yields is often not just nutrient deficiencies, but rather excesses, natural or manmade. In my observations, a significant cause of yield reduction in the bulk of farming in the central and western United States is an excess of magnesium in the soil, although many within the ag industry will claim it doesn’t make a significant difference.

To determine Mg excess, don’t look at how many pounds you have in the soil. Look at the base saturation percentage. Heavy soil may have far more magnesium in pounds than a light soil, but a heavy clay needs a lower overall percentage, and sand needs a higher percentage – on a heavy clay, Mg should be 10-12%; on lighter sand, it could ideally be as high as 20%.

The biggest limitation to me is aeration. We have to have that air. Improving soil health means building the right environment, starting with the proper amount of air and water. If we don’t have the right amount of air, we can add all the microbes, sunlight, and fertility we want, but it won’t make as much difference. Magnesium is one of the keys to aeration.

One of the first things farmers check on a soil test is the pH, but pH is not the answer – pH is an indicator. If you have a low pH, you can know you need limestone, but the composition of that lime varies depending upon if your soil is sandy or clay-based. If sandy, you generally need more emphasis on magnesium and less on calcium. If clay, you need calcium and sometimes magnesium. Often, clay soils just have a natural excess of Mg, so we try to reduce the percentage of it in the soil to have better porosity. However, Mg is not the full answer. Base saturation is principally expressed as a percentage of calcium, magnesium, potassium, sodium, and hydrogen. Apart from magnesium, two other elements that can damage porosity are potassium and sodium, and having any of these three in excess always restricts needed pore space in soil.

In clays, we need larger amounts of Ca to overcome high Mg. Calcium causes clay to gather in larger clumps or bigger particles. As clay particles are flocculated or pulled together, it increases pore space and aeration. In sandy soils, we have the opposite problem: too much air, not enough water. To get sandy ground to produce correctly, we need more Mg, less Ca.

A lot of times, you hear about the calcium-to-magnesium ratio, but in my opinion, this gives the wrong impression. If you use ratios, those don’t really apply until you’ve established your cation exchange capacity. A very productive light sandy soil will have a 3:1 Ca-to-Mg ratio, but you use Mg as a basis. In sand, if you have enough Mg, then determine the Ca you need. In heavy soils, this ratio is often more like 6.5:1 or 7:1, but again if the base you begin with is set as too high or too low, then the amount of both will still be either deficient or excessive.

What I’ve talked about so far is the long-range effects of calcium and magnesium in soil, but what about in crops? I often tell my clients that calcium and magnesium are secondary elements in a crop, but they’re the primary elements for the correction of soil. To grow a healthy crop, you need N, P, K, and S, but until you correct Ca, Mg, or both, your applications are hugely inefficient. When you look at N,P,K, and S, many farmers are putting on way more than they should need to attain their present yield goals. For example, soil has to have the proper amount of Mg before you get the correct utilization of N. This is because chlorophyll is formed as a Mg ion with N attached around it. Therefore, when you don’t have enough magnesium – and remember, 10% base saturation is the minimum for any soil – your plants won’t utilize N most efficiently. However, Mg is also the only cation that when if you have excess base saturation for a particular soil, the plant can’t get enough, either.

Tim Reinbott, who will also be speaking at Baltic in February, has shown in randomized, replicated experiments that adding adequate amounts of a soluble magnesium fertilizer will help increase corn and soybean yields when other nutrients are sufficiently present in the soil.

Tim Reinbott, who will also be speaking at Baltic in February, has shown in randomized, replicated experiments that adding adequate amounts of a soluble magnesium fertilizer will help increase corn and soybean yields when other nutrients are sufficiently present in the soil.

Corn is particularly sensitive to high Mg because it depends so much on N to make yield. Here’s an example in clay-based soils. If Mg is between 10-12% base saturation, it only takes 1 pound of N from whatever source – including humus, last year’s beans, etc. – to grow a bushel of corn. As soon as you go above 12%, then it takes 1.25 units of N to grow a bushel of corn. By the time you get to 15%, you’re at 1.35 pounds per bushel. At 18-19%, it takes 1.4. At 20, it takes 1.5 lbs./bu., just like when below 10%. So on corn, we’re usually putting on more N than we actually would need to if the Mg were at its proper level. And what’s the extra nitrogen you’re applying doing to your soil? It’s burning up humus. Then when the N converts to nitrate and doesn’t go into your crop, what happens to it? About 85% converts to nitric acid before it leaches away, attaching to Ca and depleting the soil. Then, we end up having to spend more money on more liming to correct the soil. Looking at pH alone won’t tell you that story. When you strip Ca out of the soil, something else takes its place, and much of that is Mg. For every percent calcium you lose, you gain 1% Mg., but Mg has 1.6:1 more influence on pH than Ca. For example, when we lose 400 pounds of calcium, we gain 240 pounds of Mg, but that 240 influences pH 1.6 times more than the equivalent of calcium lost. Then, if you lime back to the same pH, you have less calcium and more magnesium than you had previously. This is the trap farmers fall into when they lime to correct pH alone. This is the most ‘radical’ thing that gets some folks in ag most excited, and they will vehemently disagree with me on it. They’ll say, “pH is all you need.” Well, pH is not all you need. If it worked like pH drops based on calcium alone, it would be. But it does not.

Again, everything is relative. Do we want to maintain the status quo? Or do we want to make production as good as possible on a particular soil? We’re not just talking about getting the yields up, but getting them up with nutritional potential at the same time. As you correct soils, you’re also producing more nutritious food and fiber. So, we’re not just looking for bulk, we’re looking at what it takes to do the best job for the soil, the environment that produces the root systems, and the nutritional value of the crops themselves – how to get the top quality. Until we correct soil fertility, we don’t get the top quality. But you can get top yields AND top quality as long as you look at your ground and supply what it takes to produce those crops.

My goal with this discussion is to let you know that these problems are likely out there in your fields, and there are answers to them. With an accurate soil test and correlating that soil test to what it means in the field, that test becomes valuable and can help you make your soil and crop production more efficient. However, where soil tests fall down the most is in dealing with extreme excesses because most soil tests don’t clue you in on what to do if you run into this situation.

As you can probably tell, I can spend days talking about nutrient excesses and other fertility issues. If you want to join me for a discussion on this and other fertility topics, I will be coming to the Morton Center at the Ag PhD Field Day site near Baltic, South Dakota this coming February. If you want to talk about your soil in particular, I encourage you to send a couple samples to Kinsey Ag Services, in addition to your own typical lab, so we can compare and discuss any major differences.

Neal Kinsey Soil & Fertility Seminar
Date: February 22-24, 2022
Location: The Morton Center at the Ag PhD Field Day Site – Baltic, SD

RATES:

Pre-Registration by Sunday, February 13, 2022:

• In-person: $195 per person; $85 for each additional attendee from your farm operation (workshop book provided to in-person attendees)
• Livestream: $100/link (no workshop book included)

Registration after Sunday, February 13, 2022

• In-person: $225 per person; $95 for each additional attendee from your farm operation (workshop book provided to in-person attendees)
• Livestream: $130/link (no workshop book included)

WHAT YOU RECEIVE:

• Three days of Neal Kinsey training, normally priced at over $1500
• Seven meals (2 breakfasts, 2 suppers, 3 lunches)
• Snacks & drinks throughout the conference
• Course Book complete with Neal’s information & Ag PhD information, as well as soil tests
• Each farm receives a one-year subscription to the Ag PhD Insider Magazine
• Your agronomy and soils questions answered by Neal or Hefty agronomists during the conference. We encourage you to send at least a couple soil samples in to Kinsey Ag Services (www.kinseyag.com) prior to November 1, 2021, as well as your current soil lab, so you have your results and can ask specific questions about them during this event.
• The opportunity to visit with other farmers and agronomists about soils and more.